As an apparatus for reducing vibration noise by interference between vibration noise generated from a vibration noise source and secondary vibration noise, an active vibration noise control apparatus using an adaptive notch filter (or a single frequency adaptive notch) is known. In such an active vibration noise control apparatus, the amplitude and the phase of the secondary vibration noise can be adjusted by updating a filter coefficient of the adaptive notch filter. Although an update step size exists as a parameter for controlling an update amount of the filter coefficient, there is a case where a sudden change of the vibration noise source cannot be followed when the update step size is a constant value.
For addressing such a problem, for example, in Patent Document 1, a method is disclosed in which the update step size is changed depending on the rate of change in the frequency that vibration noise has. Further, in Patent Document 2, a method is disclosed in which the filter coefficient of the adaptive notch filter is changed based on an amplitude of the output from the adaptive notch filter just before an update.